Enterochromaffin-like cell (ECL) growth in large doses & prolonged use, excessive bacterial growth in digestive system; headache, diarrhea, abdominal pain, dyspepsia, nausea, vomiting, dry mouth, constipation, bloating, dizziness, skin rash, urticaria, pruritus; transient elevation in LFT values; arthralgia, peripheral edema, depression; thrombocytopenia, eosinophilia, leukopenia.